All three of those ports have a pipe thread in them. IIRC, it is a 3/8 NPT. Use AN flare-pipe thread adapter fittings. My IO-360-
A1A manual shows either A or C as OK for the "to cooler" port. The B port is always for oil return from cooler. Either way, the oil goes through the spin-on oil filter housing first, and the vernatherm is installed in that housing. When the Vernatherm closes,...